There have been hitherto known many microbicidal compositions. However, many of diseases caused by Oomycetes have the rapid development of disease symptom once attacked with Oomycetes, and its pathogenic microorganism spreads rapidly by secondary infection. Therefore, the diseases caused by Oomycetes are difficult to effectively control. Thus, there is a great demand for a microbicidal composition showing the superior effects of controlling the diseases caused by Oomycetes.